The Santa Clara River Watershed

The Santa Clara River flows approximately 100 miles from its headwaters near Acton, California, to the Pacific Ocean, and is one of only two natural river systems remaining in Southern California. Flowing east to west through a beautuful valley formed between the Santa Susana Mountains and the Transverse Ranges, the river crosses lands with many uses and local governments.For ease of reference, the portion of the river within Los Angeles County is generally referred to as Upper Santa Clara River, and the portion within Ventura County is generally referred to as Lower Santa Clara River. The Upper Santa Clara River watershed consists of approximately 680 square miles of mostly natural land with some mixed developed areas. Much of the development concentrates in or near the City of Santa Clarita, the lone incorporated city in the Upper Santa Clara River watershed. Some of the major tributaries to the Upper Santa Clara River watershed include Castaic Creek, San Francisquito Canyon, Bouquet Canyon, Sand Canyon, Mint Canyon and the Santa Clara River South Fork.The river supports many populations: the human communities that dot its banks, plus a great variety of flora and fauna. Extensive patches of high-quality riparian habitat, totalling over 4,000 acres, are present along the entire length of the river. The biological resources of the Santa Clara River are impressive. Downstream from Santa Clarita there are still very extensive riparian woodlands of willow and cottonwood, changing to riparian scrub in Ventura County. The river contains at least six recognized natural communities, many of which are very rare - Southern Coastal Salt Marsh, Subtidal estuarine, Southern Riparian Scrub, Cottonwood-Willow Riparian Woodland, Alluvial Fan Sage Scrub and Riverine.The riparian forest is home for a host of bird species, including the endangered least Bell's vireo. The unarmored threespine stickleback, a small endangered fish, inhabits the river's upper reaches. The estuary supports the western snowy plover, least tern and tidewater goby, all federally listed as endangered. Overall, 14 resident bird species are listed as endangered or of special concern, and 6 plant species are endangered or candidates for listing.The recent University of California publication "Gap Analysis of the Southwestern Region" examines the biological gaps in protected lands in southwest California. It states that "the Santa Clara floodplain, Sespe and Piru Canyons, and Oak Ridge to Santa Susana Mountains" represent "communities at risk" and "would seem likely candidates for extensive biodiversity management areas".Threats to the ecological health of the river include urban development, channelization, oil spills, stormwater runoff pollution, and the possible resumption of large-scale aggregate mining in the channel. In addition, we need to consider the valuable agriculture of the valley. Orchards and row crops stretch across the wider valley floor in Ventura County, extending up adjacent slopes. The California coast is the third most threatened agricultural region in the nation. The long-term protection of these rich farmlands is of great importance to society.Future uses of the river are the subject of a major study, the Santa Clara River Enhancement and Management Plan.